Echinococcosis: antibodies to echinococcus in the blood

Antibodies to echinococcus are normally absent in the blood serum.

Echinococcosis (syn.: echinococcus granulosis, cysticercus polymorphus, etc.). The skin is affected in 8% of cases. Cysts develop in the subcutaneous fat layer in the form of tumor-like formations, gradually increasing in diameter to 5-6 cm or more, hemispherical in shape, densely elastic consistency, fluctuating, translucent in transmitted light. If the echinococcus dies, the contents of the cyst undergo caseous necrosis and calcify. Sometimes, with the addition of a secondary infection, abscesses and ulcers are formed. Urticarial rashes may be observed.

Pathomorphology. Cysticercus-type changes are typical in human skin: there are many blisters in the dermis, in its lower part there is a dense leukocyte infiltrate, in which there is a cyst-like cavity filled with a large number of oval or ribbon-shaped hydatids with small hyperchromic nuclei. Among them, one can sometimes see the scolex (head), around which reactive inflammation develops with the presence of multinucleated giant cells. Subsequently, the cellular cords of the echinococcus rupture, undergo necrosis, become impregnated with calcium salts and are encapsulated.

Echinococcosis, tissue helminthiasis caused by the larval stages of Echinococcus granulosus or Echinococcus multilocularis. In humans, Echinococcus granulosus causes the formation of single-chamber cysts, mainly in the liver and lungs (hydatid echinococcosis), while Echinococcus multilocularis causes the formation of multi-chamber (alveolar) lesions (multi-chamber echinococcosis), which have the ability to invasively grow in adjacent tissues. Diagnosis of the disease presents certain difficulties. Eosinophilia is noted in less than 25% of cases.

Serological diagnostic methods have been developed for the diagnosis of echinococcosis: RPGA, RSC, latex agglutination reaction with an antigen from the fluid of echinococcal blisters and ELISA.

The most effective method for diagnosing echinococcosis is the ELISA method. However, the use of this method is limited by the fact that many carriers of echinococcal cysts do not develop an immune response, and antibodies are not formed in the blood. ELISA gives positive results in 90% of patients with cysts in the liver and only in 50-60% of patients with lung damage. High antibody titers (above 1:400) have a sensitivity of 90% and a specificity of less than 100% in cases with daughter cysts in the liver and on the peritoneum; 60% sensitivity - with lung and bone damage; 10% - false positive results (cysticercosis, collagenoses, malignant neoplasms). After surgical removal of cysts, the determination of antibodies to echinococcus in the serum is used to monitor the radicality of the operation. Disappearance of antibodies 2-3 months after surgery indicates radical cyst removal, decrease in antibody titer and its subsequent growth in the postoperative period - about cyst recurrence. In some cases, after successful surgical treatment, elevated titers can persist for years. The maximum detection of echinococcosis by the ELISA method (up to 98%) was noted when echinococcal vesicles of a living parasite are localized in the liver, abdominal cavity and retroperitoneal space, as well as in multiple and combined lesions. In case of lung damage, as well as in the presence of one to three small cysts (up to 2 cm), the effectiveness of serological diagnostics is lower and fluctuates within 70-80%. The ELISA method is the least informative for echinococcosis of the nervous (spinal cord or brain, eye), muscle or bone tissue, as well as in the case of a dead and calcified parasite (sensitivity does not exceed 40%). High antibody titers may be in patients with an active process, most often localized in the abdominal organs. In the case of pulmonary localization of the echinococcus cyst (even in the presence of a large cyst), antibody titers may be low.

Low titers of antibodies to echinococcus can be detected in the early period of the disease (cysts up to 2 cm in diameter), as well as with calcified larval cyst membranes; a sharp decrease in titers is possible in an advanced process, in the late, inoperable stage of echinococcosis.

When using serological methods for diagnosing echinococcosis, false-positive results are possible in the presence of non-specific antibodies in the blood that are similar in structure to antibodies to echinococcus. Most often, false-positive results are detected in somatic and infectious diseases accompanied by extensive destructive processes in the affected organs (liver cirrhosis, tuberculosis of the lungs and other tissues, oncological diseases). False-positive reactions are possible with other helminthiases (for example, opisthorchiasis, fascioliasis and cysticercosis).

Serological studies are used for primary diagnostics of echinococcosis, evaluation of results of surgical and conservative treatment and observation of patients in dynamics, as well as for early detection of relapses of the disease. Localization and viability of larvocysts of Echinococcus hydatidosis and alveolar, the intensity of invasion, as well as the state of the host's immune system affect the intensity of antibody formation and the detectability of the invaded using serological reactions.

Indications for serological tests:

• the presence of a volumetric formation or cysts in the liver and other organs;
• epidemiologically significant contingents - individuals classified as risk groups (hunters and their family members, livestock specialists, shepherds and herdsmen, workers in tanneries, etc.), as well as those living in echinococcosis foci.

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